“Jazz means different things at different times,” Blumenthal continues, “and as time passes, it means more.” Every generation — or at least, portions of every generation — trashes the previous one. The swingers hated bebop, the “moldy figs” of New Orleans and Chicago-style jazz thought big bands (even Duke Ellington!) were anti-jazz. “There were even people who thought King Oliver was ‘inauthentic’ because that’s not how jazz was played in New Orleans in 1916!”

To illustrate the historical slipperiness of the meaning of jazz, Blumenthal recalls what bassist Christian McBride said when asked whether Herbie Hancock’s “Chameleon,” from the 1973 Head Hunters album, was jazz: “It wasn’t then, but it is now.” “I thought that hit the nail on the head. At the time, it was a real controversy — had Herbie Hancock sold out? But now, no one would even question that ‘Chameleon’ is jazz.” Or he considers two recordings from 1964. “If you asked most jazz fans that year, ‘What is jazz?’, they would have said John Coltrane’s A Love Supreme. But if you asked a person on the street, they’d say Louis Armstrong’s ‘Hello Dolly.’ And they’d both be right!”

Blumenthal grew up in St. Louis, and he discovered jazz at age 13 when he was looking for Ray Charles’s “What I Say” in a record store. The version he bought was on an album called Ray Charles in Person, but it wasn’t the hit single. In fact, half the numbers were instrumentals. If this was jazz, it was something he wanted to hear more of, and since jazz was “serious” music, he could probably find it in the public library, like classical music. He borrowed an album recorded at the Playboy Jazz Festival that offered celebrities like Armstrong and Ella Fitzgerald but also Dizzy Gillespie, Chet Baker, and Coleman Hawkins. That led to solo records by these artists, and to books about jazz. When he was 15, a serious jazz club opened in St. Louis. Within a period of six months he had seen: the John Coltrane Quartet; the Roland Kirk Quartet; Art Blakey’s Jazz Messengers with Freddie Hubbard, Wayne Shorter, Curtis Fuller, and Cedar Walton; Dizzy Gillespie with James Moody and Kenny Barron; the Sonny Rollins Our Man in Jazz group with Don Cherry, Henry Grimes, and Billy Higgins; and the Terry Gibbs Quartet with Alice McLeod, who later became Alice Coltrane. He was on his way.

As a Harvard undergraduate, he joined WHRB, attracted by the huge record library. Senior year he got a call from a BAD editor who’d heard his show. The Boston Globe was starting a jazz festival, and the pop-music writers at the paper didn’t know jazz — Blumenthal sounded as if he knew what he was talking about. And then the editor offered a pitch familiar to freelancers everywhere: “If you are willing to write a review, we’ll give you a pair of free tickets to the festival and the assurance that all your friends will be able to read your article when we distribute the paper to the dining halls in the colleges.” A career began — one that lasted through law school and 16 years as an attorney with the state Department of Education.

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